Electrical system



E. W. PRAGST. ELECTRICAL SYSTEM.

, APPLICATION FILED lllLY 30,1920.

1,378,557. Patqnted May 17,192

' l Switch Clcses when current C' nd\,n'*e$ a predetermined time.

- Inventor} Ernest wJ ragst',

by k/ 4, M

' HisAttor ney.

UNITED S ATES PATIENT orncsi ERNEST w. rnaes'r, or scEENncrAnx NEW YORK,.AssIeNoE To GENERAL EECTRIC COMPANY, a CORPORATION or NEW YORK.

ELEcirEIoAL SYSTEM.

To all whomit'may concemr 1 Be it known that I, ERNEST W. PRAGST, a

citizen of the United States, residing at Schenectady, in the county ofSchenectady,

.- State of New York, have inventedcertaln new and useful Improvementsin'Electrical Systems, of which the following is a speci-,

' fication..

aratus for suppressing grounds orqearth aults which may occur in thesystem.

More particularly my invention'relates' t0 systems'of distributionhaving a grounded neutral connection and which has a react- 1 ancecoilin the ground connection for supl pressing. theflow of unbalancedcurrent should a fault develop.

. In systems having a grounded neutral,

Y has been the practice under certain conditions-toinsert reactance inthe grounded roper functioning of the selecting relays w ich are nowvery gen:

: r y p tribution' for cutting out feeders should a permanentfaultdevelop, such as' occurs.

when an insulator fthe line." I j v In the practice o i-my .inventionthe die advantages heretofore. attending the use of- .such reactance areavoided, for I not only. so proportion the reactor employed to theconstants of the circuit in such a manner I as toreduce the currentflowing. into a fault"- oyed in large systems "of disbecomes broken outon to a minimum,j'.but in addition provide V means-(for short circuitingthe" reactor and :hereby'dead grounding the neutral in order. to'permitthe" selecting relays v to function whenever a. fault ipersists beyonda'predeter miil ed'lengthxofftimee t I I j-theznature and objects of myinvention, reffij :erence'should'be had ;to the, following de-.

tailed description when taken in. ,conne ct1on with the accompanyingdrawing in which Figure" 1- shows diagrammatically a sys oundconnection-in accord- Speciflcation of Letters Patent.

* or a more, complete understanding function of the reactor duringthe'occurrenceof a fault.

same a Y-connectedi'source of alternating .current, such; as-a{generator or the secondaries of Y-connecte'd" transformers. The I jsource 1O is'sho"""" My inventionrelates to electrical systems oftransmission and, distribution, and has 'for" its object an improvedmethod and ap- Patented May 17, 1921.

Application filed July 30, 1920. Serialllo. 399,985.

, Referring now to the drawing, 10 repre- 14., and between the.'neutra'l' poin't off-sourcewhich is adapted. to be short circuited'bythe normally open switch 16, connected in directly to ground. theneutral of the system. The switchflti may be closed by any convenientmeans adapted 'to this end which re- I sponds toacurreiit,in.theconnection 14 that persists for a-"p eilriod ofutimedetermined bythe operator. 1' eQI'n'ean's shown for the urpose ofillustration 'comprises'ja retarde re- 10 and ground g,' "is the".reactance c'oil 1 5',

'shuntwiththe-coil 15, in order. to connect i whichfiiay besetso that;the" relay'will re spond'tol a'eurrent'thathas ersiSl fid. in con-"det'erminedej eo'n r he relay 1' bridges "the contacts 22":o1fan 1auxiliary circuit-I23 supplied ,withelectric motion 14 fQl'ixii'l'ly'fa'des'ire' period of time, for instance energy from source. 24.to'close the" circuit a s energize the trip coil'25 which actuat swhich"substantially neutralizes; hec'apaci- ,,ame. w ground-of the buses and'feedersof 'thjevsystem supplied by'source 10. This will ,be clearlcomprehended ".byreferencetbi" ".'-'Fig. .2 w ere the. capacitance'togground [of feeders 11 and-12-isdiagrammatically de'i picted'by'thecondensers 31 and-32 shown as connected in shuntiwith the feeders toground.

capacitanceof this feeder to ground during the-switch 16 toshort circuitthe @1115;

forthis feeder. Capacity current will flow during the persistence of thefault from the feeders 11 and 12 by way of the condensers 31 and 32,.asindicated by arrows a; and Z2,

into the fault A; which current is a leading current leading the EJM. F.by substantially 90 electrically. Reactive current will at the same timeflow from feeder 13 into the fault at A, as indicated by the arrow 0.This current flows back to the system by way of the ground connectionand the reactive coil 15, as indicated by the arrowc.

p The reactive current will be a lagging current, lagging behind the M.by sub stantially 90 electrically. If the coil 15 has its reactanceproportioned as prevlously stated, then the reactive current 'flowlngthrough the fault at A will be substantially equal and opposite to thecapacity current which flows through the same fault so that no arcoccurs at the fault beyond that entailed, by the negligible powercomponents of these currents. The neutralizing action of these currentsflowing through the fault at A is symbolically indicated by the arrowsa" and c", which have opposite directions.

Should, however, the fault at A persist beyond the predetermined period,of time chosen, that is the half, second in the instance mentioned,-theshort circuiting means for coil 15, symbolically depicted in Flg. 2

' at lti' will function so-that the system is then directlyconnected toground without the intervention of coil 15, or dead grounded as it isfrequently termed. W hen the system is thus dead grounded, the selectingrelays with which systems such as T have described are usually provided,but which l have not shown as they form no part of my present invention,will be permitted properly to function in order to cut out the.apnlication of my invention is not limited to -connected systems butmay be applied to any system having a neutral which is to be grounded.

Having now described an embodiment of my lnvention which is at presentthe best I -means known to me for carrying the same into effect, T wouldhave it understood that this is merely illustrative and that I do not'mean to be limited thereby to the precise details shown, nor restrictedin the choice of recognized equivalents except as defined in In claimshereunto annexed.

hat I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. The method of protecting systems of electrical transmission anddistribution which consists in connecting reactance in the connectionfrom the. neutral of the system to ground and in short circuiting thesame when a fault to ground which has developed in the system enduresmore than a predetermined period of time.

2.,The method of protecting systems of electrical transmission anddistribution which consists in connecting reactance in the connectionfrom the neutral of the System to ground proportioning said .reactancesubstantially to neutralize the ground capacitance of said system, andshort circuiting said reactance when a fault to ground has developedenduring for more than a predetermined period of time.

3. in a system of electrical transmission and distribution, thecombination 'with a source of electrical energy having a neutral point,of-a ground connection leading from said neutral point, a reactorconnected in series with said ground connection, and

means for short clrcuiting said reactor in response to currents flowingin said connection which endures more than a" predetermined periodoftime. m

i. In, a system of electrical transmission and distribution, thecombination with a source, of electrical energy having a neutral point,of a ground connection leading from said neutral point, a reactorconnected in series with said ground connection, a normally open switcharranged to short circuit" said reactor, and time delayed actuatingmeansfor said switch connected to respond to a current in saidconnection.

,5. in a system of electrical transmission and distribution, thecombination with. a source of electrical energy having a neutral point,of a ground connection leading from said neutral point, a reactorconnected in series with said ground connection, a normally open switcharranged to short circuit said reactor and provided with an actuatingwinding, and a time delayed relay arranged to respond to currents insaid connection which endure beyond a predetermined period of time, saidrelay being connected to energize said actuating winding.

- 6. in a system of electrical transmission and distribution, thecombination with a' source of electrical energy having a neutral point,of a ground connection leading from said' neutral point, a reactorconnected in serieswith said ground connection, said reactor beingproportioned to have substantially sufiicient reactance to neutralizethe capacitance to ground in the system, and means for short cirouitingsaid reactor in response to currents iiOWiIlg in said connection whichendure more than a predetermined period of time.

In a system of electrical transmission and distribution, the combinationwith a source of electrical energy having a neutral 1 point, of a groundconnection leading from said reactor, and time delayed actuating saidneutral point, a reactor connected 1n means for said switch connected torespond series with said ground connection, said to acurrent in saidconnection. 10'

reactor being proportioned to have react- In witness whereof, I havehereunto set ance substantially equal in value to the my hand this 29thday of July, 1920. ground capacitance of the system, a nor mally openswitch arranged to short circuit ERNEST W. PRAGST

